Ensure SDK credential cache type safety (#2122)

* Add the `aws-credential-types` crate

This commit adds a new crate `aws-credential-types` to the `rust-runtime`
workspace. This lays the groundwork for being able to create a
`LazyCachingCredentialsProvider` outside the `aws-config` crate according
to the proposed solution in https://github.com/awslabs/smithy-rs/pull/2082

.

We have moved the following into this new crate:
- Items in aws_types::credentials and and their dependencies
- Items in aws_config::meta::credentials and their dependencies

Finally, the crate comes with auxiliary files that are present in the
other crates in the `rust-runtime` workspace such as `external-types.toml`.

* Make `aws-types` depend on `aws-credential-types`

The credentials module has been moved from the `aws-types` crate to the
`aws-credential-types` crate. This leads to some of the items in the
`aws-types` crate adjusting their use statements to point to
`aws-credential-types`.

The `TimeSource` struct has also been moved to `aws-credential-types`
because it is used by `LazyCachingCredentialsProvider`. We have decided
to move it instead of duplicating it because `aws-config` was creating
a `TimeSource` from `aws-types` and then passing it to the builder for
`LazyCachingCredentialsProvider`. If we had duplicated the implementation
of `TimeSource` in `aws-credential-types`, two `TimeSource` implementations
would have been considered different types and the said use case in
`aws-config` would have been broken.

* Make `aws-config` depend on `aws-credential-types`

The `cache` module and modules in `meta::credentials` (except for `chain`)
have been moved to `aws-credential-types`. Again, the goal of restructuring
is to allow `LazyCachingCredentialsProvider` to be created outside the
`aws-config` crate. While doing so, we try not moving all the default
credential provider implementations.

* Make `aws-http` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Make `aws-inlineable` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Make `aws-sig-auth` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Emit `aws-credential-types` to the build directory

This commit adds `aws-credential-types` to AWS_SDK_RUNTIME so that
the build command `/gradlew :aws:sdk:assemble` can generate the crate
into sdk/build/aws-sdk.

* Make codegen aware of `aws-credential-types`

This commit allows the codegen to handle the `aws-credential-types` crate.
The items that have been moved from `aws-types` should now be prefixed with
`aws-credential-types` when generating fully qualified names.

* Make `dynamo-tests` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Make `s3-tests` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Make `s3control` depend on `aws-credential-types`

This commit adjusts the use statements for the items that have been moved
from the `aws-types` crate to the `aws-credential-types` crate.

* Update external-types.xml in rust-runtime crates

This commit fixes CI failures related to `cargo check-external-types`
in ec994be.

* Update the file permission on additional-ci

* Remove unused dependency from aws-credential-types

* Clean up features for aws-credential-types

This commit fixes a CI failure where the feature hardcoded-credentials
needed other features, aws-smithy-async/rt-tokio and tokio/rt, for the
test code to compile with --no-default-features.

* Update sdk-external-types.toml

* Update aws/rust-runtime/aws-credential-types/Cargo.toml

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-credential-types/README.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-credential-types/README.md

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-credential-types/additional-ci

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-credential-types/src/lib.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Reduce re-exports from `aws-credential-types`

This commit reduces the number of re-exports from `aws-credential-types`.
The rationale here is that if we add more items to this crate later on,
we may get some name collisions in root. Since this crate is not used by
our customers directly, it is acceptable for items to take a bit of typing
to get to.

* Fix broken intra doc link

This commit fixes a broken intra doc link that went unnoticed because the
offending link was behind the feature `hardcoded-credentials`.

* Introduce type and trait for credential caching

This commit introduces the following items in the `aws-credential-types`
crate:
* CredentialsCache
* ProvideCachedCredentials

`CredentialsCache` is a struct a user will be interacting with when creating
a credentials cache; the user no longer creates a concrete credentials cache
directly, and instead it is taken care of by `CredentialsCache` behind the
scene.
`ProvideCachedCredentials` is a trait that will be implemented by concrete
credentials caches.

Furthermore, this commit renames the following structs according to the RFC
https://github.com/awslabs/smithy-rs/pull/1842

:
* SharedCredentialsProvider -> SharedCredentialsCache
* LazyCachingCredentialsProvider -> LazyCredentialsCache

* Add `credentials_cache` to `SdkConfig` and to builder

This commit adds a new field `credentials_cache` to `SdkConfig`. It also
adds a new method `credentials_cache` to `sdk_config::Builder`. They
will help a `CredentialsCache` be threaded through from `ConfigLoader`
to a service specific client's `config::Builder`, which will be
implemented in a subsequent commit.

* Put `SharedCredentialsCache` into the property bag

This commit updates what goes into the property bag. Now that
`SharedCredentialsProvider` has been renamed to `SharedCredentialsCache`,
that's what goes into the property bag. Once a `SharedCredentialsCache`
is retrieved from the bag, credentials can be obtained by calling
`provide_cached_credentials`.

* Thread through `credentials_cache` to service client

This commit threads through `credentials_cache` to service client's
`Config` and its builder. The builder will be the single-sourced place
for creating a credentials cache.

* Update `aws-config` to use `CredentialsCache`

This commit updates `aws-config` to use `CredentialsCache`. Specifically,
* `ConfigLoader` now has `credentials_cache` to take `CredentialsCache`
* No more `LazyCachingCredentialsProvider` in `DefaultCredentialsChain`
* No more `LazyCachingCredentialsProvider` in `AssumeRoleProvider`

The second and third bullet points are a result of a credentials cache
being composed in a service client's `config::Builder` rather than
`DefaultCredentialsChain` or `AssumeRoleProvider` holding it as its field.

* Update sdk integration tests

This commit bulk updates the integration tests for SDK. Most updates
replace the previous `SharedCredentialsProvider::new` with `Arc::new`.

A more subtle but important change is to respect the `sleep_impl` field
within the build method of a Config builder, making sure to thread it
a default `LazyCredentialsCache` created within the build method. If we
missed this step, the default constructed `LazyCredentialsCache` would
later use the default Tokio sleep impl even during tests that exercise
different async runtime, causing them to fail.

* Update aws/rust-runtime/aws-credential-types/README.md

Co-authored-by: Zelda Hessler <zhessler@amazon.com>

* Rename variants of `aws_credential_types::time_source::Inner`

This commit addresses https://github.com/awslabs/smithy-rs/pull/2108#discussion_r1053637722

* Split the unit test for `time_source` into two

This commit addresses https://github.com/awslabs/smithy-rs/pull/2108#discussion_r1053638381

* Update CHANGELOG.next.toml

* Fix test failures in CI coming from `aws-inlineable`

This commit fixes test failures in CI coming from the integration test in
the `aws-inlineable` crate. Commit ea47572 should have included this
change.

* Update external-types TOML files

* Clean up offending use statements left after merging main

* Remove moved module wrongly brought in after merging main

* Remove `credentials_cache` from `Builder` for `DefaultCredentialsChain`

This commit removes a field `credentials_cache` from the `Builder` for
`DefaultCredentialsChain` as it no longer stores `LazyCredentialsCache`.
Furthermore, we have also removed methods on the builder that referred
to the field `credentials_cache`.

After this commit, certain use cases will be broken, i.e. when a user
sets timeout for loading credentials via `load_timeout` on the builder,
the configured timeout will be dropped on the floor because it will not
be threaded through the field `credentials_cache`. We will later provide
instructions for how to update those use cases with our new set of APIs.

* Remove `configure` from `LazyCredentialsCache` builder

This commit removes the `configure` method from the builder for
`LazyCredentialsCache`. We tried our best to keep it when we had moved
the builder from `aws-config` but had to modify the method signature to
destructure `ProviderCondig` to obtain the two fields out of it
(`ProviderConfig` lives in `aws-config` so cannot be passed to the builder
for `LazyCredentialsCache` which lives in `aws-credential-types`).

Given `configure` is technically meant for credentials providers, which
`LazyCredentialsCache` is not anymore, we might as well remove it and
accomplish the same effect by having customers use both `time_source` and
`set_sleep` on the builder instead.

* Update CHANGELOG.next.toml

* Update CHANGELOG.next.toml

* Use unwrap_or_else to simplify two assignments

This commit addresses https://github.com/awslabs/smithy-rs/pull/2122#discussion_r1056497419

* Add doc link to `CredentialsCache` to builder method

This commit addresses https://github.com/awslabs/smithy-rs/pull/2122#discussion_r1056500448.
In addition, it moves rustdoc for `LazyCredentialsCache` to `LazyBuilder`
as `LazyCredentialsCache` has been made `pub(crate)` from `pub` and
`LazyBuilder` is now a `pub` item instead.

* Make `CredentialsCache` configurable in `AssumeRoleProviderBuilder`

This commit addresses https://github.com/awslabs/smithy-rs/pull/2122#discussion_r1066400431.
It allows users to pass their `CredentialsCache` to the builder just as
they do in `SdkConfig`.

* Update CHANGELOG.next.toml

This commit addresses https://github.com/awslabs/smithy-rs/pull/2122#discussion_r1066400431

.

Co-authored-by: Yuki Saito <awsaito@amazon.com>
Co-authored-by: John DiSanti <jdisanti@amazon.com>
Co-authored-by: Zelda Hessler <zhessler@amazon.com>